Project Summary_________________________________________________________________________ Alcohol use disorder (AUD) affects ~17 million Americans, contributing to more than 2.5 million deaths each year in the United States alone and costing the United States $249 billion annually. Excessive alcohol drinking by individuals with AUD contributes to alcohol-related injury and death, currently the 4th leading cause of preventable death in the U.S. The neurobiological mechanisms underlying an individual?s response to alcohol, and his/her propensity to develop AUD, are not entirely understood. It is known that alcohol alters neurotransmission in mesocorticolimbic circuitry, including the ventral tegmental area (VTA), and that chronic alcohol alters neurotransmission in the central amygdala (CeA), an area involved in escalated alcohol drinking. Recent research showed that there is considerable heterogeneity among VTA dopamine (DA) neurons, and that classification of these neurons based on projection targets reveals different responses of neuronal subsets to rewarding and aversive stimuli. Important for the work proposed here, there is a functional connection between the VTA and CeA, and although each of these regions is important for addictive behavior, the role of the connection between them in addictive behaviors is unknown. The overarching hypothesis of this proposal is that VTA DA neurons projecting to the CeA are critical for mediating alcohol dependence-induced escalation of alcohol drinking. To test this hypothesis, the proposal will utilize a combination of anatomical, cellular, and behavioral techniques. This proposal will provide a promising young scientist with vital research training and professional development opportunities facilitated by experiments that use an integrative approach to test the predictions that: 1) VTA DA neurons projecting to the CeA display increased activity following repeated cycles of alcohol exposure and withdrawal, and 2) VTA DA projections to CeA mediate escalation of alcohol drinking in alcohol-dependent animals. The results of these studies will open new avenues of neuroscientific investigation exploring the crosstalk between brain reward and brain stress systems in addiction. This work may also inform development of treatment strategies for reducing escalated alcohol drinking in individuals with AUD, leading to improvements in quality of life and health of affected individuals, decreasing morbidity associated with these disorders, and potentially saving the U.S. millions of dollars in health care costs.